This was the seventh consecutive failure to accomplish a lunar soft-landing by the Soviets. On this mission, engineers redesigned the problematic I-100 guidance system that had caused most of the previous failures.

Previously, the I-100 unit had controlled both the Blok L upper stage and the spacecraft itself. On this mission (and subsequent Lunas), the fourth stage and the Ye-6 spacecraft had separate systems.

Unfortunately, this probe never reached Earth orbit. During the launch, depressurization of a nitrogen pipe for the liquid oxygen tank on the third stage had prevented third-stage engine ignition. The spacecraft broke up over the Pacific without reaching orbit.

Key Dates

10 Apr 1965: Launch

Status: Unsuccessful

Fast Facts

This was the Soviet Union's 31st deep space mission.

Engineers made improvements to a troublesome guidance system on this spacecraft, the seventh attempt at a lunar soft landing.

It is believed depressurization of a nitrogen pipe prevented the third-stage engine from firing and doomed the mission.